JPH03196763A - Facsimile equipment - Google Patents

Abstract

PURPOSE:To attain efficient facsimile communication by providing an error check means applying error check independently of each period divided by a division means and discriminating a line equalizing rate depending on error production period number. CONSTITUTION:A signal modulated by a modulator 104 is converted into an analog signal by a D/A converter 105 and excess harmonic component is extracted by a low pass filter 106 and the result is sent to a transmission line. The component other than the transmission band of the transmission signal from the transmission line is eliminated by a band pass filter 110 and controlled to a signal level processed at a receiver side by an AGC 111 and digitized by an A/D converter 112 and demodulated into an original signal by a demodulator 113. An equalizer 114 eliminates the distortion component received during transmission from the sent reception signal and a substantial transmission signal is extracted. An output signal from the equalizer 114 is sent to a discriminator 115, where a sign point is discriminated and the result is decoded by a decoder 116 and sent to a descrambler 117 and the randomized signal by a sender scrambler 101 is descrambled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a facsimile machine that performs a TCP check, for example, a facsimile machine that performs a TCP check as described in CCITT transmission control procedure T, 30 recommendation.

[Prior Art] When a facsimile machine transmits image information recorded on a transmission document via a general public line (analog line), a training signal is transmitted to the destination facsimile machine prior to transmitting the image information. The on-board modem's equalizer must be converged to eliminate the distortion received on the line.

If the line distortion is relatively small (low noise), the equalizer will converge within the training period.

However, if the line distortion is large and there is a lot of noise, the signal may not converge completely within the training period and may diverge.

In facsimile communication based on the G11ll standard, it is determined by CCI TT whether or not uniformity has converged and line distortion has been removed.
This is done based on the error rate within the TCP signal reception period specified in the transmission control procedure T.30.

Hereinafter, conventional control for determining whether line distortion has been removed will be explained along with transmission control procedures T and 30.

Figure 8 shows 7 when the training signal is successfully received.
．． 30 is a diagram illustrating a typical communication control procedure for a transmitter/reception period according to No. 30. FIG.

In the figure, 600 is a called station identification signal called CED, which is sent when automatically responding to a call from the other party, and is a signal to prompt the other party to perform a sending operation. On the called side, which is the receiving side, following CED600, 601,6
A function identification signal DIS shown in 02 for informing the other party of the CCITT standard function provided in the own device is sent.

Upon receiving the DIS signal, the calling machine, which is the transmitter, selects a mode in which communication is possible from among the receiving functions of the called party recognized by the other party's DIS shown in 603, and instructs the other party in which mode to communicate from now on. Send DO3 command.

Next, the transmitting side sends out a training signal shown at 604. The training signal consists of training and TCP (Training Check) signals. The purpose of training is to equalize line distortion and then receive the subsequent TCF normally. This training check checks the image transmission speed (
This is a signal for checking whether there is a transmission error when transmitting at a speed of, for example, 9600 bpS. This signal uses the same transmission speed and the same modulation method as the image transmission, and is transmitted continuously for 1.5 seconds.

If the called side that has received this training signal and TCP signal completes the training check normally, it will then receive a CFR (Reception Readiness Confirmation) indicating that it has successfully received TCP and is ready to receive images. signal 605
Send out. When the transmitting side receives this CFR 605, it transmits training for a predetermined period without changing the transmission speed, and then transmits the image information to be transmitted.

When transmitting image information, after the last line data of one page of images, EOL+"1" called RTC (control return signal) is issued six times to notify that no more lines will continue.

After the image information transmission is completed, the EOP shown in 607 is sent to notify the other party that the image transmission is complete and there is no next document.
(Step end) Send a signal. On the receiving side, this EOP
When receiving 607, it sends an MCF (message confirmation signal) 608 to the sender to indicate that the image has been successfully received.

Then, the transmitting side finally sends a DCN (line disconnection command) shown at 609 and ends communication with the receiving side. Note that the shaded area in the figure is a preamble, indicating that the flag sequence lasts for one second.

On the other hand, the communication control procedure when the training signal cannot be normally received by TCP during one training session during the above-mentioned control will be explained with reference to FIG.

In the same figure, 800-804 is 600-604, and 810-804 is 600-604.
Since 812 is the same control as 607 to 609, detailed explanation will be omitted.

In FIG. 9, if the training cannot be received normally in the training check at 804, the CFR signal is changed to the CFR signal shown at 605 in FIG.
Sends a TT (training failure) signal to the transmitting side, requesting it to reduce the transmission speed and send training again.

Therefore, on the sending side that receives this FTT805, the transmission speed is one step lower than the previous transmission speed (for example, if you are using a V29 modem and training was performed at 9600 bps, the transmission speed will be 7200 bps). The DC5 instruction command shown at 806 is sent so that the DC5 instruction command 806 is received.

Then, in 807, a new training signal (training + TCP) is sent at the transmission rate specified by the C3 signal.
Send.

The receiving side receives the training signal with the transmission rate reduced, and in step 808 sends a CFR to the transmitting side indicating that the TCP has been successfully received and preparations are made for image reception. In addition,
If training cannot be received normally again, 805
The control steps 807 to 807 are repeated to lower the transmission speed.

The transmitting side that receives the CFR transmits training at the transmission speed at which it received the CFR signal, and then transmits the RT after the image information.
A message with C added will be sent.

The TCP check sequence, which is the conventional criterion for determining success/failure of training in the above control, will be explained with reference to FIG.

In the figure, 300 to 302 are the transmission speeds of training signals transmitted from the transmitter side to the receiver side, and correspond to 604 in Figure 8 and 804 in Figure 9. to determine whether it is being received.

Step 300 is a check to see if the transmission rate is 9,600 bps, and if it is 9,600 bps, the variable Ni is set to 1,200 in step 303. The variable Ni is the number of data transferred from the modem to the image processing section, and in the case of a parallel interface, it is usually 8 bits per transfer, and in the case of a serial interface, it is usually 1 bit.

When the variable Ni is set to 1200, in the case of 9600 bps, this corresponds to 8 bits x 1200 = 9600 bits, that is, the amount of data for one second.

Similarly, in step 301, the transmission rate is 7200 bps.
7200b.
ps, the variable Ni is set to 900 in step 304. 7 even if the variable Ni is set to 900.
At 200 bps, this corresponds to 8 bits x 900 = 7200 bits, that is, the amount of data for one second.

In exactly the same way, in step 302, the transmission rate is 4800b.
ps, 4800 bps
If so, the variable Ni is set to 600, otherwise it is assumed to be 2400 bps, and in step 306 the variable Ni is set to 300.

After setting the variable Ni to a desired value in steps 303 to 306, in step 307 the TCP data (1, 5
A test timer (Tc) IX timer) is set to test whether a "0" continuous signal of seconds ±10% exists. Normally, the value of the TcHK timer is set to about 3 seconds. In step 308, a variable Ni is set in the data number count variable N, and the TCP check operation is started.

In step 309, a check is made to see if the verification time has elapsed. In the case of TcHK timeout, the process proceeds to step 311, sends FTT (training failure) to the transmitter side, and ends the TCP check process.

If the verification time has not elapsed, the process proceeds to step 310, and data of, for example, 1 byte is fetched from the modem section. Next, the process proceeds to step 312, where it is checked whether all 1-byte data is "0" (zero). All “0”
”, the process proceeds to step 313, where the data counter is decremented by one, and the process proceeds to step 314.

On the other hand, if all the values are not "0" in step 312, the process proceeds to step 308, and the data counter N is reinitialized to Ni.In step 314, the data counter N is set to "0".
Determine whether it has become. Transmission speed is 9600
Taking the case of bps as an example, if N=O, Ni
(1200)X8=9600 bits (=1 second) all “
Since O'' continues, it is assumed that the TCP check is OK.
Proceeding to step 315, a CFR (ready for reception) signal is transmitted to the transmitting side.

If N≠0, the process returns to step 308 and the data counter N is reinitialized to Ni.

Through the series of processes from step 308 to step 315, “0” is changed to Ni (
= 1200) If it arrives continuously for x8 bits, it is assumed that the TCP check is OK and a CFR is sent from the receiver side to the transmitter side. If not, it is assumed that the TCK check is defective and an FTT is sent. become.

[Problems to be Solved by the Invention] However, in the conventional example, as a reference for the line equalization rate, it is only checked whether "O" continues for a certain period of time during TCP reception. Therefore, even if the line equalization rate is good, if an error occurs even once due to noise such as impulse noise or instantaneous interruption, the line will fall back and it will be determined that the check is defective. He had the disadvantage of not being able to make judgments.

[Means for Solving the Problems] The present invention has been made for the purpose of solving the above-mentioned problems, and includes the following configuration as one means for solving the above-mentioned problems.

That is, it includes dividing means for dividing the TCP signal reception period into predetermined intervals equally or unequally, and error checking means for independently performing an error check for each interval divided by the dividing means.

[Operation] In the above configuration, the period for TCP check is divided into, for example, n parts, and it is verified whether or not "0" is continuously received within each period. Line equalization is performed by counting whether or not there was a reception error during the period, and if the tally result is greater than a predetermined threshold NT,4, it is considered a TCP error, and if it is smaller than N-H, it is considered a TCP reception success. This makes it possible to judge the ratio more appropriately.

[Example] Hereinafter, an example according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block configuration diagram of a facsimile machine according to an embodiment of the present invention, and 1 in the figure is a CP that controls the entire embodiment according to control procedures, etc., which will be described later, stored in a memory 2.
Reference numeral U, 2 is a memory for temporarily storing transmitted and received data, etc. in addition to the above-mentioned control procedure. 3 is a connected public episode! !
30 is a communication interface for communicating with other facsimile machines, etc., 4 is a modem, 5 is a network control unit (NCU) that controls the interface with the public line 30, 6 is a league for reading the transmitted manuscript, and 7 is received data. Ya leader 6
8 is a printer that prints out the read data, etc.; 8 is a compression/expansion unit that performs predetermined compression/expansion processing on the transmitted/received data;
Reference numeral 9 denotes an operation unit for inputting operation instructions for the apparatus.

Further, a dedicated telephone 20 is connected to the facsimile machine of this embodiment.

FIG. 2 shows the detailed configuration of the modem 4 of this embodiment having the above configuration.

The part surrounded by the chain line in FIG. 2 is the part constituted by a DSP (digital signal processing processor).

In FIG. 2, 100 and 118 are transmitting terminals and receiving terminals that are connected to the modem of this embodiment and generate digital signals to be transmitted.

101 is a scrambler that randomizes transmission data in order to prevent continuous output of the same data; 102 is an encoder that assigns a code to the signal from scrambler air o1 for each tribit, guibit, etc.; and 103 is a code amount interference of the signal. Waveform shaping filter (roll-off filter) that prevents
4 is a modulator that performs predetermined modulation processing on the signal from the waveform shaping filter 103. The modulation method in this modulator 104 is a quadrature amplitude modulation (CAM) method that changes the amplitude and phase of a carrier wave.

The signal modulated by this modulator 104 is converted into an analog signal by a D/A converter 105 to be sent to an analog public line, etc., and is further processed by a low-pass filter 106 to match the transmission band of the transmission path. harmonic components are removed and sent to the transmission line.

On the other hand, from the transmission signal from the transmission path, components outside the transmission band are first removed by a bandpass filter 110, then controlled by AGCIII to a signal level that can be handled on the receiving side, and then converted into a digital signal by an A/D converter 112. be converted into After being converted into a digital signal, it is demodulated by the demodulator 113 into the original signal before modulation. Here, reference numeral 114 denotes a container, and as will be described later, distortion components received during transmission are removed from the transmitted received signal, and the original transmitted signal is extracted.

The output signal of this flower vase 114 is sent to the determiner 115,
Here, the signal is determined to be a code point, and then decoded by the decoder 116 and sent to the descrambler 117, and the signal randomized by the scrambler 101 on the transmitting side is restored. In this way, the signal is returned to the same signal as the transmission signal output from the transmitting terminal 100, and is output to the receiving terminal 118 side.

The detailed structure and operation of the flower vase 114 in the modem device of this embodiment having the above structure will be sequentially explained.

First, the operation of the liquefaction device 114 is explained in FIGS. 3 and 4 (A) to (A).
This will be explained below with reference to C).

In FIG. 3, 6o is a transmitting modem device, 70 is a receiving modem device, 114 is the above-mentioned device built in the receiving modem device 70, and 80 is a line connecting both modem devices.

The transmission signal ak output from the transmission side modem device 60 is
As shown in FIG. 4(A), it is sent to the line 80 as a uniform gain over the entire band used. However, the line 80 has frequency characteristics, and its transmission characteristics are as shown in FIG. 4(A). B) The reception signal Rk received by the receiving modem device 20 is affected by this transmission characteristic and becomes the characteristic shown in FIG. 4(B). By providing the isometric vase 114 having the frequency characteristics shown in FIG. 4(C), the output signal akR from the isometric vase 114 has a composite characteristic of FIG. 4(B) and FIG. 4(C). The image frequency characteristics are opposite to each other, and the characteristics of the output signal a k R [characteristics obtained by convolving both characteristics (simple multiplication in the frequency domain)] are flat characteristics as shown in Figure 4 (A). As a result, distortion-free signal transmission is possible.

In other words, the role of the equalizer 114 is to create the inverse characteristics of the line characteristics.

In the method described above, line characteristics are equalized in data communications using public telephone lines, such as facsimile communications.

A detailed configuration diagram of the vase 114 that performs the above operations is shown in FIG.

The isoka 114 of this embodiment is composed of a transversal filter, and 400 in the figure is a delay element that delays received data Rk for a certain period of time, and 401 is a tap gain [C- 8~CN. As is well known, the tap gain expressed on the time axis is called a unit impulse response, and the result obtained by Fourier transformation of this is the frequency characteristic of the isoflower shown in FIG. 4(B).

Further, 402 is a multiplier that multiplies the received data delayed by the delay element 400 and the tap gain 401;
403 is an adder that takes the total value of the multiplication result of the received data delayed by the delay element 400 from each multiplier 402 and the tap gain 401;

The equalizer output signal yk with the above configuration can be expressed by the following equation.

Based on the received data, the square vase 201 calculates each tap gain using the MSE method (Mean Square Error).
It adapts to the inverse characteristics of the line by sequentially calculating the following formula according to the method.

however, γ+1 Ce =: Tap gain value calculated for the 1,000th time, ak: Judgment (estimated value) Estimated value of received data a8 and during the training period ak = ak.

L: Convergence coefficient (generally α(1) 'Ju-ak: Error signal (ek).

Note that the above-mentioned MSE method is an algorithm that minimizes the squared error signal e2.

Particularly in this modem, speed and precision of this equalization operation are required, and it is no exaggeration to say that this itself determines the performance of the modem.

In this way, the equalizer 114 creates inverse line characteristics using known data (training data) between the transmitter and receiver before data transmission, and then follows the gradual time fluctuations of the line (equalizer characteristics). ((automatic equalization or adaptive equalization)).

FIG. 6 shows an example in which the phase control section on the output side of the isometric device determination section is configured as a PLL automatic device (PLL automatic device with a square error accumulator).

R in FIG. 6 is a demodulated complex signal, which is supplied from the demodulation section of the receiving system. Reference numeral 600 denotes a line, etc., which restores data distorted on the line to its original transmission state.

・　　j　θ.

Here, Y+ = A+ e represents the first output of the isometric vase 600 in polar coordinates.

603 is a multiplier, −Jφ・of the complex number generator 605;
and output e jθ direct equalizer output Y r = e are multiplied together and -
It is output as jθl j(θ1−φ,) Z+ =Yt e =A+ e. A determiner 610 determines the code point (A1) closest to the received signal point, which is the output of the multiplier 603. A subtracter 611 subtracts the decision point from the received signal point and outputs an error signal Et=Zl-AI.

Subsequently, the error signal E1 is multiplied by the output e of the complex number generator Jφ bird 602 to obtain 1, J
φ I Exe is obtained and fed back to the flower vase 600.

J φ breath Here, e is the phase correction amount.

Next, the phase control surrounded by the dotted line in FIG. 6 will be explained.

609 is a divider which divides Z, and A, which division result,
Approximate! 1cej(θ・−φ・) is found.

608 is an imaginary part extractor which outputs sin (θ1-φ1).

sin (θ, −φi) is approximately equal to (θ1−φl) when (θ14φ, ). 606 and 607 are vCO and low-pass filters, which are the components of a normal PLL, and are used to adjust the phase value (
-φ1) is output.

Subsequently, the complex number generators 605 and 602 and the complex conjugate generator 604 output e-J$lJφ6,e, which are input to the multipliers 603 and 601, respectively, and cancel out the phase error of the entire system.

In data communications using public telephone lines, such as facsimile communications, channel equalization is performed in the manner described above.

Next, a synchronization signal (equalizer training pattern) that is actually used for channel equalization prior to transmission and reception of facsimile image data will be described below.

The table below shows CCITT as a training pattern for the equalizer.
, V29 Recommendation, and with reference to this table, C
I will explain fall pack using the CITT V29 recommendation as an example.

Note that segment 1 in the table is a transmission preparation period after segment 2 in which no carrier is transmitted. Segment 2 is a pattern for timing phase alignment, and is a period for alternately transmitting constellation patterns and -tones specified in the V29 recommendation, and for setting basic reception operating conditions such as AGC and timing extraction. Segment 3 is an equalizer adjustment pattern for the purpose of initial setting of the equalizer, and a pseudo-random pattern is used to enable rapid convergence of the equalizer. Segment 4 is a period for transmitting an output signal when 1 is input to the scrambler and establishing synchronization of the descrambler.

The table shows synchronization signals recommended by V29, which are used to equalize line characteristics before transmitting and receiving facsimile image data. Following the synchronization signal, a continuous signal of 0° for 1.5 seconds ±10% called TCP (Training Check) is sent to confirm whether the line characteristics have been properly equalized.

Therefore, the transmitter side first sends out a synchronization signal having a transmission rate of 9600 bps, and then sends out TCP.

On the receiver side, AGC control, timing extraction, and equalizer adjustment are performed while receiving the synchronization signal.

Next, during the TCP period, for example, 1 second is checked to see if there are any errors, and if there is an error, the transmitter side is sent the FTT (
) training failure) and falls back to 7200 bps. If there is no error, a CFR (receipt confirmation signal) is sent to the transmitter side, and image data is transmitted and received at the same transmission speed as the reception synchronization signal, 9600 bps, without fallback.

TCP check control in the facsimile machine of this embodiment having the above configuration will be explained below with reference to the flowcharts of FIGS. 7A and 7B.

The following explanation is for 5 seconds ± 10% during the TCP signal reception period.
), one second is divided into three equal parts.

In FIGS. 7A and 7B, steps 400 to 4
02 is step 300 to step 3 in FIG. 10 mentioned above.
Since the control is exactly the same as 02, detailed explanation will be omitted.

In step 403, since the transmission speed is 9600 bps, the variable Ni is set to r400J. This is 96
Since the transmission speed is 00bps, it is 1/1 of 9600bps.
This is because 3200 bits corresponding to the amount for 3 seconds = 400×8 bits.

(Similarly, in the case of 7200 bps, step 404
Set r300J to the variable Ni.

This is a transmission rate of 7200bps, so 7200bps
2400 bits equivalent to 1/3 second of bps =
This is to make it 300×8 bits. In the case of 4800 bps, in step 405, the variable Ni is set to r200J and 2
In the case of 400 bps, in step 406 the variable Ni is set to r.
Set loOJ.

Since the variable Ni will be the initial value of the data counter in the following explanation, the above setting will check whether there is any error over each equally divided period having a length of 1/3 second.

Following steps 403 to 406, which are the initial setting of the variable Ni, the process proceeds to step 407 in any case and waits until TCP is received.

Here, if TCP is received, the process advances to step 408. In step 408, a loop counter LC is set to "3" for performing the same processing during three equally divided periods. Subsequently, in step 409, an error counter EC for checking how many of the three equally divided periods an error has occurred is initialized to "O". Next, in step 410, an error flag that is set when an error occurs in each equally divided period is initialized to "0" prior to the series of processing.

Then, in step 411, steps 403 to 4 are performed.
The variable Ni set in step 06 is set in the data counter N.

Now that the check preparation is complete, continue (Step 4).
At step 12, one byte of data is input from the data line 121 of FIG. 2 mentioned above. Then, in step 413, it is determined whether or not the input data contains a value other than "O" (whether an error has occurred). If no error has occurred, the process proceeds to step 415 without doing anything.

If a value other than "0" is included and an error has occurred, the process proceeds to step 414, where the error flag EFLG is set and the process proceeds to step 415.

In step 415, the data counter N is decremented by one. In the following step 416, the data is checked for 1/3 second to determine whether the data counter N has become "0". If the data counter N is not 0 and 1/3 second has not elapsed, the process returns to step 412 and repeats the series of data input and error checking processes.

On the other hand, when the data counter N becomes "0", l/
Since 3 seconds have elapsed, the process advances to step 417 to check whether an error has occurred and the error flag EFLAG has been set. No error occurred and error flag EFLA
When G is "0", the process proceeds to step 419 without doing anything.

When the error flag EFLAG is set to “1”,
Since an error has occurred, the process proceeds to step 418, where the value of the error counter EC is incremented by one, and the process proceeds to step 419.

In step 419, the loop counter LC is decremented by one because the one-division period processing has ended. Then, in the following step 420, it is determined whether all the processing for the three equally divided periods has been completed and the loop counter LC has become 0. If the loop counter LC is not "0" and there is a divided period that has not been processed. Then, the process for the next divided period should be executed (proceed to step 410).

On the other hand, if the loop counter LC is "0" and the processing of all divided periods has been completed, the process advances to step 421;
The error counter EC has a predetermined threshold value NT)I (In this embodiment, NTH=1, but this threshold value can be arbitrarily determined).

) is greater than. That is, the error is 1
Determine whether the period in which the event occurred twice or three times.

If the error occurs two or three times, it is assumed that it is a TCP error and the process proceeds to step 423, instructing the transmitter to send an FTT via the modem 4 to fall back. The series of processing is completed, and the next TCP after fallback is performed again.

On the other hand, if the error period is 0 or 1, it is assumed that TCP has succeeded, and the process proceeds to step 422, where the CFR is sent to the transmitter side via the modem 4 to inform the transmitter that the training has been successful. Therefore, from now on, facsimile image communication is performed at the transmission speed used during training.

As explained above, according to this embodiment, there is no need to fall back due to the transmission characteristics of the line, and even though TCP was originally successful, TC happened to be interrupted due to external noise etc.
Even when an error occurs during F, unnecessary retraining, fallback, and other processes can be effectively prevented, and efficient facsimile communication becomes possible.

[Other Embodiments] The above explanation is based on an example in which 1 second of a TCP signal (1.5 seconds ± 10% continuous °゛O'') is divided into three equally divided sections. Of course, the time is not limited to one second, and may be any time within the TCP period.

Furthermore, the equally divided sections are not limited to three equally divided sections (of course, they may be n equally divided sections, or even n unequal divided sections).

Further, although the above explanation has been made using an example of using an 8-bit parallel interface as an interface between modems and facsimile devices, the present invention is not limited to the above example, and can also be used with an n-bit parallel interface. , a serial interface is also fully applicable.

As described above, the application of the present invention is not limited to the embodiments, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

As explained above, according to this embodiment, the standard for the line equalization rate is simply 0" during TCP reception, unlike the conventional
Instead of checking whether the reception period has been continuous for a certain period of time, the reception period is divided into equal or unequal divisions, and it is checked whether there is an error in each period and whether there is an error in the total period. The line equalization rate is determined based on whether the total value is larger or smaller than a certain threshold, so even if there are some sections where errors occur due to noise such as impulse noise or instantaneous interruptions, the If the number of sections does not reach the threshold, TCP is considered successful, so it is now possible to make a more appropriate judgment on the line equalization rate.

[Effects of the Invention] As explained above, according to the present invention, there is no need to perform a fallback due to line transmission characteristics (despite originally being TCP successful, noise such as impulse noise or instantaneous interruption) Even if an error occurs during TCF due to the Communication becomes possible.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment according to the present invention, Fig. 2 is a detailed configuration diagram of the modem of this embodiment, Fig. 3 is a diagram for explaining the flow of transmission signals in this embodiment, and Fig. 4. (A) is a diagram showing the frequency characteristics in the line, Figure 4 (B) is a diagram showing the frequency characteristics in the isoflower, and Figure 4 (C) is a diagram showing the frequency characteristics of the transmission signal from the transmitting modem and corrected by the isohan. FIG. 5 is a diagram showing the configuration of the equalizer of the modem of this embodiment. FIG. 6 is a schematic diagram of equalization operation using the equalizer of this embodiment. FIGS. 7A and 7B are The TCF check control flowchart of this embodiment, FIG. 8 shows CCITT, T, in case of successful training.
A conventional typical control flowchart between a transmitter and a receiver according to No. 30, FIG. 9 shows CCITT in case of training failure, T,
FIG. 10 is a typical conventional control flowchart between a transmitter and a receiver according to 30, and FIG. 10 is a conventional TCP check control flowchart. In the figure, 1...CPU, 2...Memory, 3...Communication interface, 4...Modem, 5...Network control unit (NCU), 6...League, 7...Printer , 8・
...Compression/expansion section, 9...Operation section, 20...
- Dedicated telephone, 60... Sending modem, 80... Line, 70... Receiving modem, 100... Sending terminal,
101... Scrambler, 102... Encoder, 10
3... Pulse shaping filter, 104... Modulator, 1
05...D/A converter, 106...Low pass filter, 110...Band pass filter, 111...A
GC1112...A/D converter, 113...Demodulator, 114,600...Vase, 115...Judgment device,
116...Decoder, 117...Descrambler,
118... Receiving terminal, 400... Delay element, 401
... Tap gain, 402 ... Multiplier, 403 ...
・It is an adder. Figure

Claims (2)

[Claims] (1) It is characterized by comprising a dividing means for equally or unequally dividing the TCF signal reception period into predetermined intervals, and an error checking means for independently performing an error check for each interval divided by the dividing means. facsimile machine. (2) The error check means checks the number of sections in which errors have occurred, and determines the line equalization rate based on whether the number of sections in which errors have occurred is larger or smaller than a predetermined threshold. facsimile machine.